Thermal conductivity near the bottom of the Earth's lower mantle: Measurements of pyrolite up to 120 GPa and 2500 K
Thermal conductivity near the bottom of the Earth's lower mantle: Measurements of pyrolite up to 120 GPa and 2500 K
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DOI：
10.1016/j.epsl.2020.116161
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发表时间：
2020-04
影响因子：
5.3
通讯作者：
Z. Geballe;N. Sime;J. Badro;P. V. van Keken;A. Goncharov
中科院分区：
文献类型：
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作者：
Z. Geballe;N. Sime;J. Badro;P. V. van Keken;A. Goncharov
摘要地幔矿物的热导率是理解地核向地幔热输运的关键。在地球的核幔边界的压力-温度条件下，基于原子模型的晶格热导率的计算已经确定了范围从1到14 W/m/K的硼镁石和富硼镁石矿物组合的值。以前的研究是在室温下进行的，直到核幔边界的压力，但将这些校正到地热温度可能会引入很大的误差。在这里，我们提出的地幔矿物晶格热导率的第一次测量的压力和温度附近的地幔底部，120 GPa和2500 K。我们使用连续和脉冲激光加热相结合的金刚石对顶砧单元来测量地幔岩的晶格热导率，预计组成下地幔的矿物组合。我们发现在80 GPa和2000 ~ 2500 K时的值为3.9+ 1.4− 1.1 W/m/K，在124 GPa和2000 ~ 3000 K时的值为5.9+ 4.0− 2.3 W/m/K。这些数值排除了地球中下地幔热导率的最高计算值（即在80 GPa下k< 6 W/m/K），并且与下地幔底部附近热导率的高值和低值计算值一致。
Abstract Knowledge of thermal conductivity of mantle minerals is crucial for understanding heat transport from the Earth's core to mantle. At the pressure-temperature conditions of the Earth's core-mantle boundary, calculations of lattice thermal conductivity based on atomistic models have determined values ranging from 1 to 14 W/m/K for bridgmanite and bridgmanite-rich mineral assemblages. Previous studies have been performed at room temperature up to the pressures of the core-mantle boundary, but correcting these to geotherm temperatures may introduce large errors. Here we present the first measurements of lattice thermal conductivity of mantle minerals up to pressures and temperatures near the base of the mantle, 120 GPa and 2500 K. We use a combination of continuous and pulsed laser heating in a diamond anvil cell to measure the lattice thermal conductivity of pyrolite, the assemblage of minerals expected to make up the lower mantle. We find a value of 3.9+ 1.4− 1.1 W/m/K at 80 GPa and 2000 to 2500 K and 5.9+ 4.0− 2.3 W/m/K at 124 GPa and 2000 to 3000 K. These values rule out the highest calculations of thermal conductivity of the Earth's mid-lower mantle (ie k< 6 W/m/K at 80 GPa), and are consistent with both the high and low calculations of thermal conductivity near the base of the lower mantle.